package com.eatme.core.queue;

public class LoopQueue<E> implements Queue<E> {

    private  E[] data;

    private int front,tail;

    private  int size;

    public LoopQueue(int capacity) {
        data = (E[])new Object[capacity+1];
        front =0;
        tail =0;
        size =0;
    }

    public LoopQueue() {
        this(10);
    }

    public int getCapacity() {
        return data.length-1;
    }


    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return front == tail;
    }

    @Override
    public void enqueue(E e) {
        if ((tail+1)%data.length==front)
            resize(getCapacity()*2);
        data[tail] =e;
        tail = (tail+1)%data.length;
        size++;
    }

    private void resize(int newCapacity) {
        E[] newData = (E[])new Object[newCapacity+1];
        for (int i = 0; i < size; i++)
            newData[i] = data[(i+front)%data.length];
        data = newData;
        front =0;
        tail = size;
    }

    @Override
    public E dequeue() {
        if (isEmpty())
            throw  new IllegalArgumentException("Cannot dequeue from an empty queue.");
        E ret = data[front];
        data[front] =null;
        front = (front+1)%data.length;
        size--;
        if (size==getCapacity()/4 && getCapacity()/2 != 0)
            resize(getCapacity()/2);
        return ret;
    }

    @Override
    public E getFront() {
        if (isEmpty())
            throw new IllegalArgumentException("Queue is empty.");
        return data[front];
    }

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append(String.format("LoopQueue: size = %d, capacity = %d\n",size,getCapacity()));
        stringBuilder.append("front [");
        for (int i = front; i!=tail; i=(i+1)%data.length) {
            stringBuilder.append(data[i]);
            if ((i+1)% data.length!=tail)
                stringBuilder.append(", ");
        }
        stringBuilder.append("] tail");
        return stringBuilder.toString();
    }

    public static void main(String[] args) {
        LoopQueue<Integer> loopQueue = new LoopQueue<Integer>();
        for (int i = 0; i < 10; i++) {
            loopQueue.enqueue(i);
            System.out.println(loopQueue);
            if (i % 3 == 2) {
                loopQueue.dequeue();
                System.out.println(loopQueue);
            }
        }
    }
}
